Safety primer for blasting



Aug. 19, 1947. H. B. HUMPHREY 2,425,741

' SAFETY PRIMER FOR BLASTING Filed April 23, 1945 71911. I M j; '7

Patented Aug. 19, 1947 vour!"so ST TES I A T- 70 FREE 1 1 Claim.

The invention described herein may be manufactured and used by or forthe Government of the United States for governmental purposes withoutth'epayment-to-me-of any royalty thereon in' accordance with theprovisions of the act of April 30, 1928 (Ch. 460, 45 Stat. L. 467) Thisinvention relates to the art of blasting, but more particularly to asafety primer for blasting, and has for its object to provide acartridge which includes provision for protecting the detonator and itsattached wires or fuse and in which the detonator will be centered inthe most favorable position for maximum detonating effect and to providea safety primer which can be used an where in the charge in the drillhole.

With these objects in view, the invention consists of the novelconstruction of the molded dynamite cartridge and in the provision of afrangible protecting tubular member, all of which will first be fullydescribed and afterwards specifically pointed out in the appended claim.

Referring to the accompanying drawing:

Fig. 1 is a vertical longitudinal sectional view of a blasting cartridgeconstructed in accordance with my invention and having an electricallywired detonator.

Fig. 2 is a vertical transverse sectional view through the same taken online 22 of Fig. 1.

Fig. 3 is an elevation partly in vertical section of the frangibleprotecting tube and its molded dynamite end plug.

Fig. 4 is an elevation partly in vertical section of a blastingcartridge constructed in accordance with my invention and having a fuseigniting detonator, and

Fig. 5 is an elevation partly in vertical section of the frangibleprotecting tube and its molded dynamite end plug for the fuse type ofcartridge shown in Fig. 4.

Like numerals of reference indicate the same parts throughout theseveral figures, in which:

The primer consists of a molded dynamite cartridge I, made in twosections 2 and 3 as shown in Fig. 1.

In the main section '2 of the cartridge I there is a centeredcylindrical chamber 4 to receive a suitable detonator 5.

Formed on the smaller or plug section 3 of the cartridge is a frangibleprotecting tube 6 made of incombustible material such as finely groundclay, limestone, talc or the like, which is bound together suflicientlyto hold its form and shape while being handled and assembled andpositioned for use, but sufiiciently frangible to break amended Aprilso, 1928; .3700. G. 757-) 1 I and spread apart when firm tampingpressure is applied as is necessary to fill up the bore hole.

In the form of cartridge shown in Figs. 1, 2 and 3, wherein an electricdetonator is employed, the frangible shell 6 has twodiametricallyopposite longitudinally positioned slots 1 to receive the detonatorwires 8 and 9, as shown in Figs. 1 and 2, while the plug section 3 ofthe cartridge is reduced at H] to form a shoulder II to receive the endof the frangible shell 6.

When the detonator 5 is inserted in the central chamber 4 and the wires8 and 9 are lying along the outside of the main portion 2 of thecartridge, the plug section 3 of the cartridge with its attachedfrangible shell 6 is slipped over the cartridge section 2 with itsinserted detonator 5 so that the wires 8 and 9 lie in the longitudinalslots 1 of the frangible shell 6, as shown in Figs. 1 and 2, and betweenthe abutting end faces of the two cartridge sections 2 and 3.

The main cartridge member 2 may be enveloped in a wrapping ofwater-proof paper l2, before the parts are assembled, and if desired,the frangible shell 6 and the plug section 3 of the cartridge maylikewise be wrapped with paper M.

In the construction shown in Figs. 4 and 5, the frangible shell 6 is notprovided with the longitudinal slots 1 but is cylindrical; In thisexample, the plug section 3 has a channel l5 which extends from itsouter surface IS on an inclination to the center thereof, as shown inFig. 4. The fuse I! for the detonator 5 lies in this inclined channel l5and thence along the bore hole so that there are no sharp turns or bendsin the fuse I! which would be likely to interfere with or impair itsefiiciency in operation. The detonator 5 and fuse H are passed throughthis inclined channel l5 before the detonator 5 is inserted in itschamber 4 in the main section 2 of the cartridge. The plug section 3 andattached frangible shell 6 are then slipped over the end of the maincartridge section 2 containing the detonator 5, as shown in Fig. 4.

Havin thus described the invention, the cartridge is placed in positionby the application of firm tamping pressure. The frangible protectiveshell 6 resists pressure in line with the axis of the bore hole, butsplits when extra pressure is applied so that the shell 6 will bepressed against the walls of the bore hole and the dynamite of thecartridge will be forced in around the detonator to aiford itprotection. Tendency of the detonator to turn at an angle is obviated,while the frangible shell provides a cushion for the detonator inaddition to that provided by the x 3 dynamite. The frangible shell 6 isdesigned to split and spread under pressure so as to allow compactingthe explosive in the bore-hole and to hold the primer in bore-holes thathave a steep angle above the horizontal.

Having thus described the invention, I do not wish to be understood aslimiting myself to the exact construction shown and described, asvarious changes may be made therein, and I consider myself clearlyentitled to all such changes and modifications as fall within the limitand scope of the appended claim.

I claim:

A safety primer for blasting which includes two sections of moldedexplosive in abutment with each other, the end of one section which isin the said protective shell of readily frangible material beingprovided with longitudinal slots to receive wires leading to thedetonator, the whole arranged whereby the said protective shell ofreadily frangible material is sufiiciently stable to hold the twoabutting sections of molded explosive in proper assembled positionduring handling and insertion of the primer in a bore hole but uponapplication of firm tamping pressure exerted on the primer will splitand be expanded against the wall of the bore hole to close the bore holeand retain the primer explosive and its detonator in proper positionthereon.

HIRAM B. HUMPHREY.

REFERENCES CITED ihe following references are of record in the file ofthis patent:

UNITED STATES PATENTS

